Train Warning Horn

The warning horn is used to communicate and despite only having a few settings, can tell us a lot about the movement taking place. Some units have multiple settings (high/low/loud/soft) The unit in the video is a Class 150/2 DMU with 2 settings - High and low.

If two tones are provided, you must use the horn as shown below. If the horn has no soft/loud setting, you must use the setting provided.

Circumstances Tones you must use:
To give a warning to anyone on or near a running line = High and low tones - use the loud setting

To give an urgent warning to anyone on or dangerously near to the line = High tone - use the loud setting

When passing a whistle board = Low tone - use the loud setting

To give a warning when in a depot or siding = Low tone - use the soft setting

To sound a local or special code = High tone - use the loud setting

Wrong-direction movements = High tone - use the loud setting

a) Anyone on or near the line - You must sound the horn to warn anyone who is on or near the line on which you are travelling. Give a series of short, urgent danger warnings to anyone who is on or dangerously near the line who does not:
• acknowledge your warning by raising one arm above the head,
or
• appear to move clear out of the way of the train.

b) Whistle boards (W Boards)
You must only sound the horn when passing a whistle board between 0600 and 2359, except in an emergency or when anyone is on or near the line.

c) Within a possession - You must sound the horn on starting your train when making a movement within a possession.

d) Wrong-direction movements - When making a wrong-direction movement on a running line for which there is no signal provided, you must sound a series of short blasts at frequent intervals.

e) Train movements - You must sound the horn at any other time you consider necessary.

[mozomenku]

You can even see the pressure lightly reducing.

[DistrictDriver]

When I was driving (years ago) the two-tone was always used, but these days it seems most drivers just use a single tone. I assume there's been some rule change? I was taught that the two tone was to differentiate from a normal one-tone air horn on a road vehicle.

[ldvlogs]

Judging by the cab layout and the horn lever it looks to be a northen unit?